The present invention relates to disc drive data storage systems and, more particularly, to a disc drive data storage system having a slider with an increased bearing stiffness for ramp load-unload and other applications.
Disc drives of the “Winchester” and optical types are well known in the industry. Such drives use rigid discs, which are coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor, which causes the discs to spin and the surfaces of the discs to pass under respective hydrodynamic (e.g. air) bearing disc head sliders. The sliders carry transducers, which write information to and read information from the disc surfaces.
An actuator mechanism moves the sliders from track-to-track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each head gimbal assembly. The suspension includes a load beam and a gimbal. The load beam provides a load force which forces the slider toward the disc surface. The gimbal is positioned between the slider and the load beam, or is integrated in the load beam, to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc.
The slider includes a bearing surface, which faces the disc surface. As the disc rotates, the disc drags air under the slider and along the bearing surface in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the bearing surface, air compression along the air flow path causes the air pressure between the disc and the bearing surface to increase, which creates a hydrodynamic lifting force that counteracts the load force and causes the slider to fly above or in close proximity to the disc surface.
In ramp load-unload applications, the disc drive further includes a ramp positioned at an outer diameter of the disc for engaging the suspension. When the disc drive is powered down, the actuator mechanism moves the head gimbal assembly radially outward until the suspension engages the ramp, causing the slider to lift off of the disc surface. During power-up, the disc is accelerated to its normal operating velocity and then the actuator mechanism moves the head gimbal assembly radially inward such that the suspension disengages the ramp allowing the slider to become loaded on to the disc surface.
Using a ramp to load and unload the head gimbal assembly to and from the disc surface has been regarded as an attractive alternative to “contact start/stop” technology in which the slider lands and takes-off from a dedicated zone on the disc surface. The ramp load-unload technique can be used for solving tribological problems associated with lower fly heights and for meeting severe requirements of non-operational shock performance. However, this technique introduces an array of other challenges, such as possible severe head-media impact during loading and unloading operations.
Under nominal conditions, advanced air bearings (AABs) can be designed to avoid head-media contact during load and unload. Manufacturing of actual parts, however, introduces deviation from nominal conditions, which can result in larger susceptibility to impact during load-unload operations. Among the numerous dimensions and geometrical features to be controlled during manufacturing, pitch static angle (PSA) and roll static angle (RSA) are the most critical parameters for load-unload applications. PSA is the angle formed between the slider and the suspension in a direction parallel to the suspension's axis of symmetry when no air bearing is formed (i.e., in a “static” state). RSA is the angle formed between the slider and the suspension in a direction perpendicular to the suspension's axis of symmetry. Since PSA and RSA have an influence on the pitch and roll attitude of the slider during flight, a non-optimal PSA or RSA results in the slider tilting with respect to the radial motion of the suspension during loading and unloading operations. Under these conditions, it is possible that edges or corners of the slider can become close enough to the media to induce light contact or severe impact. This contact can cause damage to stored data and can cause permanent physical damage to the media.
A slider is desired, which increases the load-unload robustness by preventing or reducing head-media contact over an acceptable range of manufacturing deviations in RSA and PSA from nominal RSA and PSA values.